Extraction of zinc.



H. L. SULMAN L H. F. K. PICARD.

EXTHACTION OF ZINC. APPL'lCATlON FILED JAN.20. 1917 ,i295,080 PatentedFeb.1s,1919.

@f6/rayne Z076.

HENRY LIvINGsToNE sULMaN AND HU LoNDoN, ENGLAND, AssIGNoRs To LIMITED,or LONDON, ENGLAND.

GH FITZALIS KIRKPATRICK PICARD, 0F

THE METALS EXTRACTION CORPORATION EX'IRACTION 0F ZINC.

Letters Patent Patented Een. is, rara.

Application led January 20, 1917. Serial No. 143,448.

To all whom t may concern: y

Be it known that we, HENRY LIVINGSTONE SUL'MAN,`a subject of the King ofEngland, and HUGH FITzALrs KIRKPATRICK PICARD, a subject of the King ofEngland, both residing at London, England, have invented certain new anduseful `Improvements in the Extraction of Zinc, `of which the followingis a specification.

This invention is for improvements in or relating' to the extraction ofzinc from ores or zinc-containing materials, and it refers moreparticularly to the preparation of a solution of zinc by dissolving themetal from the ore or other material containing it with an acid. It hasfor its object to overcome certain diiiicultieswhich are met With incarrying out such a process.

It has previously been proposed to treat a zinc ore or zinc-containingmaterial with an acid such as sulfuric acid to dissolve the zinc andform a solution thereof for treatment by electrolysis. In such a processthe orc, if a sulfid ore, must be first roasted to convert the sulfidinto oxid.

In extracting' zinc from an ore or zinccontaining material with acid adifficulty is experienced in completely neutralizing the acid with whichthe ore is treated, and thereinthe form of roasted fore in fullyextracting the zinc from the ore added thereto. For example if asolution containing 10% of acid has "zinc oxidv zinc-bearing ore addedto it in quantity theoretically sufficient to neutralize all the acid,it is found that complete neutralization is not readily obtained, thelast portions of acid. remaining unneutralized even after agitation forsome time with an excess of roasted ore. In practice the additions ofroasted ore to acid solution are made in successive small quantities,with vigorous agitation; but such neutralization is not eicient below 1or 2% of residual free sulfuric acid, and when approaching this limit itis preferable that the mixture be agitated for longer periods than werenecessary for the previous ore additions to the stronger acid solution.l lt is also an object ofthe Vpresent invention to overcome thisdifliculty, and according to this invention the. neutralization of thelast portions of the acidl with Whichthe ore is treated is quicklycompleted bythe addition of zinc hydrate.4 l.

`One method df carrying this invention intoeffect will now be describedwithreference to the accompanying drawing which represents the processdiagrammatically for the production of a zinc salt solution forsubsequent treatmentby electrolysis. A' zinc sulfid-.containing oreis'roasted to convert the yzlnc into oxid and partially sulfate, and

after grinding is added in successive portions to a 10% solution ofsulfuric acid. When after such additions in'kdue amounts the liquor isfound offree acid, the neutralization is completed by the addition ofthe requisite quantity of zinc hydrate obtained in the manner 4describedbelow. The mixture is submitted 'to a short agitation to neutralizecompletely the acid. Where soluble silica is present the solution -isApreferably agitated and maintained at a temperature of from 90 to 100C., so that the soluble silica is caused to be precipitated in a moregranular form whereby it is prevented from /ge'latinizing and fromcausing' trouble in filtration or even the complete jellication of theliquor. The solid material is then separated from the liquor in afilter-press or vacuum or other suitable filtration apparatus, `and theclear liquor may be passed over lgranulated metallic zinc, or preferablyagitated with zincfume, to remove any copper and cadmium present.

The material left in the ltenpress is the ore, viz. silica undissolvedportion of the gangue-stulf, linsoluble lead and other Inetalliccompounds, ferrie oxid, gelatinous silica', etc., but still wetted withsome strong zinc sulfate solution.

This is recovered as with water, but the zinc sulfatesolution soobtained is necessarily too Weak and too voluminous to be added t0 themain bulk of the filtra-te, which in a cyclic -electrolytic proc-v ess,must be kept'at the `strength'. and volume suitable for the finalelectrolytic precipitation of the zinc; from 8% to 10% of zinc assulfate is a desibe electrolyte. In order to prevent the accu `ulationof large quantities of these weak liquors and to avoid y to contain from1 to 2% usual by washing-out the necessity of concentrating themandtheir zinc contents by evaporation, We Atreatthem in a suitable tank orvesselwith strong agi-4 tation with the requisite quantity of milkvwhereby zinc vhydrate and calcium 0f lime.

v'of the copper present'is submitted to velectrolysis for the p "jseparation of the zinc until the solution con- 25 f is returned for thetreatment of a fresh quansulfate are precipitated. The pulp is thenfiltered, the Water now free from zinc being run to Waste. zinc hydrate,which is very readily soluble even' in dilute acid, thus forms anexcellent material for completing the neutralization of an'originalmixtureof ore and, acid which cannot, as stated, be completely orefficiently neutralized by roasted ore additions; and

tains about 10% ofv sulfuric acid, When it tityof roasted ore toneutralize its acid content andreplenish its zinc.

' Various modifications may be made in the process Without departingfromthis inven-f tion. For example if alcarbonate ore is to be treated,it is not necessary to submit it containing material include zinc ores.l A 1 What We claim. as our invention and deto a preliminaryroast beforetreatment with the acid. 'y

In the following claims the term zincis to be understood to sire tosecure byLetters Patent is 1.- In aprocess for the extraction of zinc Ifrom zincfcontaining material treating the l lteringl the clearsolutions from the residue, l

material'with acid to dissolve the zinc,

The precipitate containing to 'be re-l Washing the residue to remove thesolution remaining therein, adding milk of linie to thel said Washingsto precipitate zinc hydrate and adding the precipitate so obtained tothe solution produced from a fresh-batch of zincco'ntaining material'bytreatment with acid to (omplete quickly the neutralization of the aciQ2. Ina process for the extraction of zinc from zinc-containing materialin Which the materia-l is treated with an acid, complet-- ing theneutralization of the acid by the Aaddition to the solutions of zinchydrate andV agitating the vmixture of zinc-containing liquor andmaintaining it at a temperature of from 90 to 100o C. to causethegelatinous silica to separate in 3. In a process for the extraction ofzinc from zinc-containing material treating the material with acid todissolve the zinc', ing zinc hydrate to neutralize quickly the remainingacid, agitating the mixture and maintaining it at a temperature ofrom`90 to 100o C. to cause the gelatinous silica to. separate, theresidue, Washing the residue to remove the solution remaining therein,adding milk of lime to the said Washings to precipitate `zinc hydrateand adding the precipitate so obtained to the solution produced from afresh batch of zinc-.containing material by treatment with acid tocomplete quicklytheneutralization of the acid;

In testimony whereof We have signed oui` names to this specificationinthe presence of two subscribing Witnesses. v A

HENRY LiviNGsroNi. siiiiiiiii'.A HUGH riTziLis KiiiKrirRicK riolen.

Witnesses:

ALFRED l\liri"rii -1e,r HERBERT S, BURSLEY.

a more granular orm.-

material residue and neutralized ada y

